JP2018179679A - Radiation shield material - Google Patents
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Abstract
Description
本発明は、Ｘ線やγ線等の放射線を遮蔽する機能を有する放射線遮蔽材料に関する。詳しくは、フッ化物の固溶体を含み、透明樹脂に充填した際に、優れた透明性と高い放射線遮蔽効果を実現することが可能な放射線遮蔽材料を提供するものである。 The present invention relates to a radiation shielding material having a function of shielding radiation such as X-rays and γ-rays. More specifically, the present invention provides a radiation shielding material which contains a solid solution of fluoride and can realize excellent transparency and high radiation shielding effect when filled in a transparent resin.
放射線を発生する放射性物質からの放射線を遮蔽する機能を有する放射線遮蔽材料は、成形容易な樹脂に配合し、放射性物質が収容される各種の構造物、例えば容器、パイプ、防具、シリンジ、壁材等に成形して使用に供される場合が多い。 Radiation shielding materials having the function of shielding radiation from radioactive materials that generate radiation are incorporated into easy-to-mold resins, and various structures in which radioactive materials are accommodated, such as containers, pipes, armor, syringes, wall materials There are many cases where it is used after being formed into an etc.
放射線遮蔽材料としては、鉛や鉛ガラスが代表的であるが、これ以外にも、タングステンなどの金属、硫酸バリウムなども知られており、さらに、本出願人により提案された特許文献１には、フッ化バリウム等のフッ化物が、放射線遮蔽性に優れていることが開示されている。 As a radiation shielding material, lead and lead glass are representative, but in addition to this, metals such as tungsten, barium sulfate and the like are also known, and further, Patent Document 1 proposed by the present applicant It is disclosed that fluorides such as barium fluoride and the like have excellent radiation shielding properties.
ところで、放射性物質が収容される各種の構造体においては、構造体内部に収容されている放射性物質の状態を視認するために透明性が要求される場合が多い。また、メガネなどのように、構造体自体に視認性が要求され、このような構造体に放射線遮蔽性が要求されることもある。このような透明性が要求される用途に使用される構造体は、透明性を有する樹脂に放射線遮蔽材料が配合されて成形されるが、樹脂が有する透明性を維持するために、用いる樹脂の種類に応じて屈折率が樹脂に近い放射線遮蔽材料を選択する必要がある。例えば、放射線遮蔽性の構造体の形成に使用される樹脂について、比較的安価に入手できる透明樹脂の屈折率は、一般に１．４０〜１．５５の範囲にあり、この屈折率に近い放射線遮蔽材料を選択することとなる。 By the way, in various structures in which a radioactive substance is accommodated, transparency is often required in order to visually recognize the state of the radioactive substance accommodated in the structure. In addition, the structure itself may be required to have visibility, such as glasses, and such a structure may be required to have radiation shielding properties. The structure used for applications requiring such transparency is formed by blending a radiation shielding material with a resin having transparency, but the resin used to maintain transparency of the resin. Depending on the type, it is necessary to select a radiation shielding material whose refractive index is close to that of the resin. For example, for resins used to form radiation shielding structures, the refractive index of transparent resins, which can be obtained relatively cheaply, is generally in the range of 1.40 to 1.55, and radiation shielding close to this refractive index You will be selecting the material.
ここで、放射線遮蔽材料の放射線遮蔽性は、一般に、密度が大きい程、放射線遮蔽性が大きい。一方で、放射線遮蔽材料の屈折率は、一般に、密度が大きい程、屈折率が大きい。したがって、大きな密度を有し、放射線遮蔽性に優れた放射線遮蔽材料の屈折率は、前記放射線遮蔽性の構造体の形成に使用される樹脂の屈折率を超えて大きくなり、放射線遮蔽材料と樹脂の屈折率を互いに近似させて、透明な放射線遮蔽性の構造体を得ることが困難であった。このため、放射線遮蔽性の高い放射線遮蔽材料と、屈折率が小さな放射線遮蔽材料との固溶体を使用することにより、放射線遮蔽材料の屈折率を、用いる樹脂の屈折率に近づけるという手段が開示されている（特許文献１参照）。 Here, the radiation shielding property of the radiation shielding material is generally larger as the density is higher. On the other hand, the refractive index of the radiation shielding material is generally higher as the density is higher. Therefore, the refractive index of the radiation shielding material having a large density and excellent radiation shielding property becomes larger than the refractive index of the resin used to form the radiation shielding structure, and the radiation shielding material and the resin It is difficult to obtain transparent radiation shielding structures by approximating the refractive indices of. For this reason, by using a solid solution of a radiation shielding material having a high radiation shielding property and a radiation shielding material having a small refractive index, a means is disclosed to make the refractive index of the radiation shielding material close to the refractive index of the resin used. (See Patent Document 1).
しかしながら、上記のような手段を採用した場合、樹脂の屈折率に近づけるために、屈折率の小さな放射線遮蔽材料を固溶せしめて屈折率の大きな放射線遮蔽材料の屈折率を低下させると、それに伴って密度が低下し、その結果、放射線遮蔽性の低下が生じてしまう。 However, when adopting the means as described above, if the radiation shielding material having a small refractive index is made into a solid solution to lower the refractive index of the radiation shielding material having a large refractive index in order to approach the refractive index of the resin Density, which results in a decrease in radiation shielding.
従って、本発明の目的は、高い密度を有しながら、屈折率が透明樹脂に近い範囲に抑えられた放射線遮蔽材料を提供することにある。 Therefore, an object of the present invention is to provide a radiation shielding material which has a high density while the refractive index is suppressed in the range close to the transparent resin.
本発明者等は、屈折率が互いに異なる放射線遮蔽材料を組み合わせたときの屈折率について検討した結果、密度が異なるフッ化物の固溶体において、固溶体の密度に対し、予想外の屈折率の低下挙動を示す組合せが存在するという知見を得た。かかる知見に基づき更に研究を重ねた結果、従来の放射線遮蔽材料において実現されていなかった、鉛ガラスに相当する高い遮蔽性を実現可能な密度を有しながら、屈折率を透明樹脂の屈折率の上限以下に抑えた放射線遮蔽材料の開発に成功し、本発明を完成させるに至った。 As a result of examining the refractive index when radiation shielding materials having different refractive indexes are combined, the present inventors unexpectedly reduced the refractive index with respect to the solid solution density in a solid solution of fluoride having different densities. It has been found that the combination shown is present. As a result of further research based on such findings, it has been found that the refractive index of the transparent resin is equal to that of the transparent resin while having a density capable of achieving high shielding properties equivalent to lead glass, which has not been realized in conventional radiation shielding materials. We succeeded in the development of the radiation shielding material suppressed below the upper limit, and came to complete the present invention.
本発明によれば、密度が６ｇ／ｃｍ３以上、屈折率が１．５５以下であるフッ化物の固溶体を含むことを特徴とする放射線遮蔽材料が提供される。 According to the present invention, there is provided a radiation shielding material comprising a solid solution of fluoride having a density of 6 g / cm 3 or more and a refractive index of 1.55 or less.
本発明の放射線遮蔽材料においては、前記フッ化物の固溶体は、フッ化イッテルビウムとフッ化ストロンチウムとの固溶体であることが好ましい。
また、本発明によれば、前記放射線遮蔽材料を、透明樹脂１００質量部に対して、１００質量部以上の割合で充填した放射線遮蔽材が提供される。
In the radiation shielding material of the present invention, the solid solution of fluoride is preferably a solid solution of ytterbium fluoride and strontium fluoride.
Further, according to the present invention, there is provided a radiation shielding material in which the radiation shielding material is filled in a proportion of 100 parts by mass or more with respect to 100 parts by mass of the transparent resin.
本発明の放射線遮蔽材料は、高い密度による放射線遮蔽効果を有しながら、低い屈折率を実現している。従来、放射線遮蔽材料として硫酸バリウムが用いられているが、その密度は４．５ｇ／ｍｌとさほど高くない上に、その屈折率は１．６４であり透明樹脂の屈折率の上限１．５５より高い。また、比較的高い密度を有する物質として、二酸化ジルコニウム（密度 ５．７ｇ／ｍｌ）が用いられるが、その屈折率は２．１３であり透明樹脂の屈折率の上限１．５５より遙かに高く、透明樹脂に添加した際に高い透明性を実現することができない。これに対して、本発明の放射線遮蔽材料は、透明樹脂に充填して高い放射線遮蔽能を有しながら、高い透明性を有する放射線遮蔽材を得ることが可能である。 The radiation shielding material of the present invention achieves a low refractive index while having a high density radiation shielding effect. Conventionally, barium sulfate is used as a radiation shielding material, but its density is not so high as 4.5 g / ml, its refractive index is 1.64, and the upper limit of the refractive index of transparent resin is 1.55. high. In addition, zirconium dioxide (density 5.7 g / ml) is used as a substance having a relatively high density, but its refractive index is 2.13, which is much higher than the upper limit 1.55 of the refractive index of transparent resin. When added to a transparent resin, high transparency can not be realized. On the other hand, the radiation shielding material of the present invention can be filled in a transparent resin to obtain a radiation shielding material having high transparency while having high radiation shielding ability.
本発明の放射線遮蔽材料は、複数のフッ化物、一般には、二種のフッ化物からなる固溶体を含むことを特徴とする。上記固溶体は、複数のフッ化物が互いに溶け合い、全体が均一の結晶相となっているものをいい、例えばＸＲＤ測定によると、前記均一な結晶層に基づく特有のピークを示すものであり、所謂、混合物とは異なる。混合物の場合には、それぞれのフッ化物に基づくピークが個別に観察される。
本発明の放射線遮蔽材料において、固溶体におけるフッ化物の組合せは、密度が高い（屈折率が高い）フッ化物Ａと密度が低い（屈折率が低い）フッ化物Ｂとからなる。
上記密度が高い（屈折率が高い）フッ化物Ａとしては、密度が６．５ｇ／ｃｍ３以上、好ましくは、７ｇ／ｃｍ３以上のフッ化物が好適である。具体的には、フッ化イッテルビウム、フッ化ルテチウム、フッ化ハフニウム、フッ化鉛等が挙げられる。中でも、密度が高く、比較的安価に入手でき、且つ環境負荷が小さいフッ化イッテルビウムが好ましい。
一方、密度が低い（屈折率が低い）フッ化物Ｂとしては、密度が３〜５．５ｇ／ｃｍ３のフッ化物が好適である。具体的には、フッ化ストロンチウム、フッ化バリウム、フッ化イットリウム等が挙げられる。
上記フッ化物の組合せにおいて、密度が大きなフッ化物Ａと密度が小さなフッ化物Ｂとは、密度差が１．２ｇ／ｃｍ３以上あるものが推奨され、特に、フッ化イッテルビウムとフッ化ストロンチウムとの組合せが好ましい。
本発明の放射線遮蔽材料において、フッ化物の固溶体は、一般に、密度が大きなフッ化物Ａに密度が小さなフッ化物Ｂを固溶せしめたものであって、該固溶体の密度はフッ化物Ａの密度に比較して小さくなる。ここで、本発明で用いるフッ化物の固溶体は、かかる密度の低下に比較して、屈折率が予想外に低下するという特徴的な挙動を示す。このことは、本発明では、固溶体において、密度の低下、即ち放射線遮蔽性の低下を抑えながら、屈折率を大きく低下できることを示している。
上記のような屈折率の特異的な挙動は、屈折率及び密度が異なる２種のフッ化物を選択し、これらを固溶化させることにより生じる特有の現象である。かかる現象は、多くの実験により見出された現象であり、その理由については明確に解明されているわけではないが、本発明者等は、次のように推定している。
即ち、物質の屈折率はその密度と誘電率に依存する。屈折率及び密度が大きいフッ化物Ａと屈折率及び密度が小さいフッ化物Ｂを固溶化すると、密度が低下するばかりでなく、誘電率も大きく低下し、その結果、固溶体の屈折率は、固溶体の密度低下に比較して大きく低下したものとなるのではないかと、本発明者等は推定している。
例えば、フッ化物以外の化合物については、上記のような現象は確認されていない。フッ化物以外の化合物について、屈折率及び密度が異なる２種の化合物を選択して固溶化させたとしても、おそらく、誘電率の低下が無いか或いは小さいためではないかと考えられる。
The radiation shielding material of the present invention is characterized by containing a plurality of fluorides, generally a solid solution consisting of two kinds of fluorides. The solid solution is a solution in which a plurality of fluorides dissolve into one another to form a uniform crystalline phase as a whole. For example, according to XRD measurement, it exhibits a characteristic peak based on the homogeneous crystalline layer, It is different from the mixture. In the case of mixtures, each fluoride based peak is observed separately.
In the radiation shielding material of the present invention, the combination of fluorides in the solid solution consists of high density (high refractive index) fluoride A and low density (low refractive index) fluoride B.
As the fluoride A having a high density (high refractive index), a fluoride having a density of 6.5 g / cm 3 or more, preferably 7 g / cm 3 or more is suitable. Specifically, ytterbium fluoride, lutetium fluoride, hafnium fluoride, lead fluoride and the like can be mentioned. Among them, preferred is ytterbium fluoride, which has high density, can be obtained relatively inexpensively, and has low environmental impact.
On the other hand, a fluoride having a density of 3 to 5.5 g / cm 3 is preferable as the fluoride B having a low density (a low refractive index). Specifically, strontium fluoride, barium fluoride, yttrium fluoride and the like can be mentioned.
In the above combination of fluorides, it is recommended that the fluoride A with a large density and the fluoride B with a small density have a density difference of 1.2 g / cm 3 or more, and in particular, ytterbium fluoride and strontium fluoride Combinations are preferred.
In the radiation shielding material of the present invention, the solid solution of fluoride is generally a solution of fluoride A having a high density and fluoride B having a low density, and the density of the solid solution is the density of fluoride A. It becomes small compared with. Here, the solid solution of fluoride used in the present invention exhibits a characteristic behavior in which the refractive index is unexpectedly lowered as compared to the decrease in density. This indicates that, in the present invention, in the solid solution, the refractive index can be greatly reduced while suppressing the decrease in density, ie, the radiation shielding property.
The specific behavior of the refractive index as described above is a unique phenomenon caused by selecting two kinds of fluorides having different refractive indexes and densities and making them form a solution. Such a phenomenon is a phenomenon found by many experiments, and the reason is not clearly understood, but the present inventors estimate as follows.
That is, the refractive index of a material depends on its density and dielectric constant. When the fluoride A having a large refractive index and density and the fluoride B having a small refractive index and a density are dissolved, not only the density is reduced but also the dielectric constant is largely reduced. As a result, the refractive index of the solid solution is The present inventors have estimated that the density is significantly reduced compared to the density reduction.
For example, the above phenomenon has not been confirmed for compounds other than fluoride. Even if two types of compounds different in refractive index and density are selected and dissolved for compounds other than fluoride, it is considered that there is probably no decrease in dielectric constant or a small amount.
本発明の放射線遮蔽材料において、固溶体は、前記現象を利用して、密度が６ｇ／ｃｍ３以上、屈折率が１．５５以下であるフッ化物の固溶体を実現する。かかる固溶体において、前記フッ化物Ａとフッ化物Ｂの選択とその割合は、上記範囲となる組合せ、割合であれば、特に制限されない。一般には、固溶体とした場合の密度の低下と屈折率の低下を確認して上記範囲を満足する固溶体を使用すればよい。
因みに、前記フッ化イッテルビウムとフッ化ストロンチウムとの固溶体について、最適な割合は、フッ化イッテルビウムが７０〜８０ｍｏｌ％である。
In the radiation shielding material of the present invention, the solid solution realizes a solid solution of fluoride having a density of 6 g / cm 3 or more and a refractive index of 1.55 or less, using the above phenomenon. In the solid solution, the selection of the fluoride A and the fluoride B and the ratio thereof are not particularly limited as long as they are combinations and ratios that fall within the above range. In general, it is sufficient to use a solid solution that satisfies the above range by confirming the decrease in density and the decrease in refractive index in the case of a solid solution.
Incidentally, the optimum ratio of the solid solution of ytterbium fluoride and strontium fluoride is 70 to 80 mol% of ytterbium fluoride.
本発明において、上述した固溶体は、フッ化物Ａとフッ化物Ｂとを所定の質量比で混合し、加熱して溶融した後に冷却固化することにより容易に得られる。
得られた固溶体は、適宜粉砕し、必要に応じて、メッシュ等での選別を経て、所定の粒径（例えば平均粒子径が数μｍ〜数百μｍ、具体的には、２〜３００μｍ）となるように粒度調整して放射線遮蔽材料として使用に供される。
In the present invention, the above-mentioned solid solution is easily obtained by mixing fluoride A and fluoride B in a predetermined mass ratio, heating and melting, and then cooling and solidifying.
The obtained solid solution is appropriately pulverized and, if necessary, sorted with a mesh or the like to obtain a predetermined particle size (for example, an average particle size of several μm to several hundred μm, specifically 2 to 300 μm). The particle size is adjusted so as to be used as a radiation shielding material.
本発明では、前記フッ化物の組合せにおいて、密度低下を抑えながら低い屈折率を確保することができるため、この放射線遮蔽材料は、密度が６ｇ／ｃｍ３以上、屈折率が１．５５以下の従来に無い特性を示し、例えば、高い遮蔽効果を維持しながら透明樹脂との屈折率差を０．０７以下、好適には０．０５以下、さらに好適には０．０３以下の範囲に調整することができる。
かかる放射線遮蔽材料は、透明性を有する樹脂に配合され、樹脂組成物として所定形状に成形され、例えば放射性物質が収容された構造体、例えば、各種容器、パイプもしくはホース、シリンジ、採光用窓、保護メガネ、その他、放射線遮蔽板もしくはシート等の形態で使用される。これにより、樹脂の透明性を維持し、これら部材の視認性を確保することができる。
In the present invention, since the low refractive index can be secured while suppressing the density decrease in the combination of the fluorides, the radiation shielding material according to the prior art has a density of 6 g / cm 3 or more and a refractive index of 1.55 or less. The difference in refractive index with the transparent resin is adjusted to a range of 0.07 or less, preferably 0.05 or less, more preferably 0.03 or less while maintaining a high shielding effect. Can.
Such a radiation shielding material is compounded in a resin having transparency, formed into a predetermined shape as a resin composition, for example, a structure containing a radioactive substance, such as various containers, pipes or hoses, syringes, windows for lighting, It is used in the form of protective glasses, other, radiation shielding plates or sheets. Thereby, transparency of resin can be maintained and visibility of these members can be secured.
この放射線遮蔽材料が配合される透明性を有する樹脂としては、前述したフッ化物Ａ，Ｂを用いての屈折率調整によって、より近い範囲に近似可能な１．４０〜１．５５の屈折率を有するもの、例えば、エポキシ樹脂、塩化ビニル樹脂、アクリル樹脂、シクロオレフィン樹脂、シリコーン樹脂、ポリエステル樹脂、ポリ（メタ）アクリレート樹脂、ポリスチレン樹脂、ポリカーボネート樹脂などが好適であり、これらは必要に応じてブレンドされていてもよい。特に、透明性を損なわずに、放射線遮蔽性を維持できるという点で、ポリエチレンテレフタレート等のポリエステル樹脂が最も好適に使用される。 As a resin having transparency to which this radiation shielding material is compounded, a refractive index of 1.40 to 1.55 which can be approximated to a closer range by the refractive index adjustment using the fluorides A and B described above For example, epoxy resin, vinyl chloride resin, acrylic resin, cycloolefin resin, silicone resin, polyester resin, poly (meth) acrylate resin, polystyrene resin, polycarbonate resin, etc. are suitable, and these may be blended according to need. It may be done. In particular, polyester resins such as polyethylene terephthalate are most preferably used in that radiation shielding properties can be maintained without impairing the transparency.
尚、上記の放射線遮蔽材料は、樹脂の成形性等を損なわない範囲において、所望の放射線遮蔽性が得られるに十分な量、例えば、樹脂１００質量部当り４０質量部以上の量で樹脂にブレンドされる。特に優れた放射線遮蔽性を得るためには、放射線遮蔽材の充填量を、樹脂１００質量部当り１００質量部以上とすることが好ましく、２００質量部以上とすることが特に好ましい。
ブレンドの手段としては、それ自体公知の方法を採用することができ、例えば、バンバリーミキサーや押出機等を用いて樹脂を加熱溶融させながら放射線遮蔽材料を混練して樹脂組成物を調製することができる。
また、得られた樹脂組成物は一旦ペレット状等に固化させた後に成形機により成形することもできるし、樹脂の溶融を維持した状態で成形することもできる。成形方法としては、射出成形、押出成形、プレス成形、カレンダー成形、ブロー成形等公知の方法を採用することができる。
The above radiation shielding material is blended with the resin in an amount sufficient to obtain a desired radiation shielding property, for example, an amount of 40 parts by mass or more per 100 parts by mass of the resin, as long as the moldability of the resin is not impaired. Be done. In order to obtain particularly excellent radiation shielding properties, the filling amount of the radiation shielding material is preferably 100 parts by mass or more, and more preferably 200 parts by mass or more per 100 parts by mass of the resin.
As a means for blending, a method known per se can be adopted, and for example, a radiation shielding material is kneaded while heating and melting the resin using a Banbury mixer, an extruder or the like to prepare a resin composition it can.
Further, the obtained resin composition can be once molded in a pellet form or the like and then molded by a molding machine, or can be molded in a state where melting of the resin is maintained. As a molding method, known methods such as injection molding, extrusion molding, press molding, calendar molding, blow molding and the like can be adopted.
さらに、この放射線遮蔽材料が配合された樹脂組成物には、透明性或いは放射線遮蔽性が損なわれない範囲において、可塑剤、熱安定剤、酸化防止剤、帯電防止剤、滑剤、加工助剤等を、着色剤等を配合することもできる。
本発明の放射線遮蔽材料は、密度が６ｇ／ｃｍ３以上と高いため、これを透明樹脂に配合して極めて高い遮蔽性を有する放射線遮蔽材を得ることができる。例えば、２ｍｍの厚みの板状放射線遮蔽材において、０．５ｍｍ以上の鉛当量を実現でき、５ｍｍの厚みの板状放射線遮蔽材において、１ｍｍ以上の鉛当量を実現できる。
尚、鉛当量とは、ある放射線遮蔽材について、これと等価な遮蔽能を与える鉛の厚みをいい、鉛当量が高いほど、放射線遮蔽性に優れる。例えば、鉛当量が１ｍｍの放射線遮蔽材は、厚み１ｍｍの鉛板と等価な放射線遮蔽性遮断性を有する。
Furthermore, in the resin composition containing this radiation shielding material, a plasticizer, a heat stabilizer, an antioxidant, an antistatic agent, a lubricant, a processing aid, etc. insofar as the transparency or the radiation shielding property is not impaired. It is also possible to blend a coloring agent and the like.
Since the radiation shielding material of the present invention has a high density of 6 g / cm 3 or more, it can be blended with a transparent resin to obtain a radiation shielding material having extremely high shielding properties. For example, in a plate-shaped radiation shielding material having a thickness of 2 mm, a lead equivalent of 0.5 mm or more can be realized, and in a plate-shaped radiation shielding material having a thickness of 5 mm, a lead equivalent of 1 mm or more can be realized.
In addition, about a certain radiation shielding material, a lead equivalent means the thickness of the lead which provides the shielding ability equivalent to this, and it is excellent in radiation shielding property, so that a lead equivalent is high. For example, a radiation shielding material having a lead equivalent of 1 mm has a radiation shielding property equivalent to a lead plate having a thickness of 1 mm.
本発明の優れた効果を次の実験例により説明する。
尚、以下の実験に用いた各種の測定は、以下の方法により行った。
The excellent effects of the present invention will be described by the following experimental examples.
In addition, the various measurements used for the following experiments were performed by the following methods.
屈折率の測定；
屈折率は、固溶体の粉末を試料とし、屈折率が既知の標準液に試料を分散させ、最も透明となる標準液の屈折率を試料の屈折率とした。該標準液は、屈折率が１．３０〜１．８０の範囲で、０．０１刻みで規定されたものが市販されており、容易に入手できる。
密度の測定；
密度は、固溶体の粉末を試料とし、比重瓶を用いて、日本工業規格 ＪＩＳ Ｚ ８８０７：２０１２に準じて測定した。即ち、比重瓶の質量 Ｍ０、試料を入れた比重瓶の質量 Ｍ１、更に標準物質として水を加えて比重瓶を満たしたときの質量 Ｍ２を測定し、加えた標準物質の質量 ｍ１（ｍ１＝Ｍ２−Ｍ１）を求めた。標準物質だけで比重瓶を満たしたときの質量 Ｍ３を測定し、試料と同体積の標準物質の質量 ｍ２（ｍ２＝Ｍ３−Ｍ０−ｍ１）を求めた。試料の質量 ｍ０（ｍ０＝Ｍ１−Ｍ０）と、ｍ２と標準物質密度とによって計算される試料の体積から試料の密度を求めた。
Measurement of refractive index;
For the refractive index, a solid solution powder is used as a sample, the sample is dispersed in a standard solution whose refractive index is known, and the refractive index of the standard solution that is most transparent is used as the sample refractive index. The standard solutions having a refractive index in the range of 1.30 to 1.80, which are defined in 0.01 increments, are commercially available and readily available.
Measurement of density;
The density was measured according to Japanese Industrial Standard JIS Z 8807: 2012 using a solid solution powder as a sample and using a pycnometer. That is, the mass M0 of the pycnometer, the mass M1 of the pycnometer containing the sample, and the mass M2 when water is added as a standard substance to fill the pycnometer, the mass M1 of the standard substance added (m1 = M2 It asked for-M1). The mass M 3 when the pycnometer was filled with only the standard substance was measured, and the mass m 2 (m 2 = M 3 −M 0 −m 1) of the standard substance of the same volume as the sample was determined. The sample density was determined from the sample volume calculated by the sample mass m0 (m0 = M1-M0), m2 and the standard substance density.
＜実験例１＞
フッ化物Ａとして、フッ化イッテルビウム（ＹｂＦ３、密度８．２、屈折率１．６０）の粉末を用意し、フッ化物Ｂとしては、フッ化ストロンチウム（ＳｒＦ２、密度４．２、屈折率１．４４）の粉末を用意した。
ＹｂＦ３の粉末とＳｒＦ２の粉末を、７５：２５のモル比で混合し、フッ化イッテルビウムが７５ｍｏｌ％の混合物を得た。該混合物を溶融し、次いで固化することにより、放射線遮蔽材料として使用される固溶体を調製した。
得られた固溶体を粉砕機によって細かく粉砕し、目開き２００μｍの篩にかけ、篩下分を回収し固溶体の粉末を得た。該粉末の平均粒子径は１０６μｍであった。
得られた固溶体の粉末について、密度と屈折率を測定した結果、それぞれ７．２ｇ／ｍｌ及び１．５３であった。密度は、前記混合比から算出される算術平均値、即ち８．２×０．７５＋４．２×０．２５＝７．２と一致しているのに対し、屈折率は、前記混合比から算出される算術平均値、即ち１．６０×０．７５＋１．４４×０．２５＝１．５６に比較して大きく低下していることが分かる。
得られた固溶体の粉末 ８００ｇと、屈折率が１．５４の液状のシリコーン樹脂 １００ｇを混練し、真空脱泡により気泡を除去した。得られた固溶体粉末と液状シリコーン樹脂の混合物を厚さが５ｍｍで１００ｍｍ×１００ｍｍのモールドに注入し、シリコーン樹脂を加熱硬化させて５ｍｍの厚さを有する１００ｍｍ×１００ｍｍの放射線遮蔽材を得た。該放射線遮蔽材の全光線透過率は９０％であり、優れた透明性を有していた。
得られた放射線遮蔽材について、放射線遮蔽能を測定した結果、鉛当量が１．５ｍｍであり、鉛ガラスに比肩する放射線遮蔽性を有することが分かった。
Experimental Example 1
As the fluoride A, a powder of ytterbium fluoride (YbF 3 , density 8.2, refractive index 1.60) is prepared, and as the fluoride B, strontium fluoride (SrF 2 , density 4.2, refractive index 1) The powder of .44) was prepared.
The powder of YbF 3 and the powder of SrF 2 were mixed at a molar ratio of 75:25 to obtain a mixture of 75 mol% of ytterbium fluoride. The solid solution used as a radiation shielding material was prepared by melting and then solidifying the mixture.
The obtained solid solution was finely pulverized by a pulverizer, passed through a 200 μm mesh sieve, and the sieve fraction was recovered to obtain a powder of a solid solution. The average particle size of the powder was 106 μm.
The density and refractive index of the obtained solid solution powder were measured and found to be 7.2 g / ml and 1.53, respectively. The density corresponds to the arithmetic mean value calculated from the mixing ratio, that is, 8.2 × 0.75 + 4.2 × 0.25 = 7.2, while the refractive index is calculated from the mixing ratio. Compared to the calculated arithmetic mean, that is, 1.60 × 0.75 + 1.44 × 0.25 = 1.56.
800 g of the obtained solid solution powder and 100 g of a liquid silicone resin having a refractive index of 1.54 were kneaded, and air bubbles were removed by vacuum degassing. A mixture of the obtained solid solution powder and liquid silicone resin was poured into a 100 mm × 100 mm mold having a thickness of 5 mm, and the silicone resin was heat cured to obtain a 100 mm × 100 mm radiation shielding material having a thickness of 5 mm. The total light transmittance of the radiation shielding material was 90%, and had excellent transparency.
The radiation shielding ability of the obtained radiation shielding material was measured, and as a result, it was found that the lead equivalent is 1.5 mm and the radiation shielding property is comparable to that of lead glass.
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